Medical treatment of some illnesses requires continuous drug infusion into various body compartments, which is carried out as subcutaneous and intra-venous injections. For example, diabetes mellitus patients require the administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as a superior alternative to multiple daily injections of insulin. These pumps, which deliver insulin at continuous basal rates as well as in bolus volumes, were developed to liberate patients from repeated self-administered syringe injections, and allow them to maintain a near-normal daily routine. Both basal and bolus volumes must be delivered in precise doses, according to individual prescription, since an overdose of insulin could be fatal. Therefore, insulin injection pumps must feature high reliability, to prevent the unintentional delivery of an excess of insulin.
Several ambulatory insulin infusion devices are currently available on the market. Mostly, these devices have two parts: a durable portion, containing a pumping mechanism, a controller and electronics, and a disposable portion containing a reservoir, a needle/penetrating assembly (e.g., a cannula and penetrating/needle member), and a fluid delivery tube altogether referred to as the “infusion set”. Usually, the patient fills the reservoir, attaches the infusion set to the exit port of the reservoir, and then inserts the reservoir into the pump housing. After purging air out of the reservoir, out of the tube and out of the needle, the patient inserts the needle assembly, penetrating member and cannula, at a selected location on the body, and withdraws the penetrating member while leaving the cannula within the body. To avoid irritation and infection, the subcutaneous cannula must be replaced and discarded after two to three days, together with the empty reservoir.
Examples of a first generation pump, which employs disposable syringe-type reservoir and tubes, were described in 1972, by Hobbs, in U.S. Pat. No. 3,631,847, and in 1973, by Kaminski, in U.S. Pat. No. 3,771,694, and later by Julius, in U.S. Pat. No. 4,657,486, and by Skakoon, in U.S. Pat. No. 4,544,369, each of which is incorporated by reference herein. The driving mechanism employed in these devices comprises a screw thread derived plunger controlling the programmed movement of a syringe piston. While these devices represent an improvement over multiple daily injections, unfortunately they are heavy, bulky, and must be carried in a pocket or attached to a belt. Consequently, the fluid delivery tube is long, usually more than 60 cm, to permit needle insertion in remote sites of the body. Furthermore, since the tubing is long and not discreet, this severely disturbs teenagers' body image and prevents the teenager patients from insertion in remote sites like buttocks and limbs. To avoid the tubing limitations, a second generation of insulin pump was devised, namely—skin adhered pumps. For the sake of brevity these pumps will be referred-to further as patch type pumps or simply patches.
These patches include a housing having a bottom surface adapted for contact with the patient's skin, a reservoir disposed within the housing, and an injection needle which is in fluid communication with the reservoir. These skin adhered devices should be disposed every 2-3 days like current pump infusion sets. This type of pump was described by Schneider, in U.S. Pat. No. 4,498,843, Burton in U.S. Pat. No. 5,957,895, Connelly, in U.S. Pat. No. 6,589,229, and by Flaherty in U.S. Pat. No. 6,740,059, each of which is incorporated by reference herein. Additional configurations of skin adhered pumps are disclosed in U.S. Pat. Nos. 6,723,072 and 6,485,461, which are incorporated by reference herein. In these configurations, the pump is adhered to the patient's skin for the entire time period of device usage and the needle emerges from the bottom surface of the device and is fixed to the device housing.
These second-generation skin adhered devices have several limitations:                Disconnection and reconnection of the pump to the patient is impossible—while there exists several conditions such as hot showers, bath and sauna (cause insulin denaturation) as well as other activities during which disconnection of the pump is required. In some cases the patient wants to disconnect the pump for a short period and subsequently reconnect it just to free himself from the 24 hours a day/7 days a week life long connection.        Waste of Insulin—In cases of site misplacement (scar tissue, bleeding, cannula kinking etc.) the entire device including reservoir, which is full of insulin should be disposed.        These devices are expensive—the entire device including relatively expensive parts should be disposed every pump replacement. Thus the production cost is high and the final product price far exceeds Medicare allowable payments.        These devices are bulky and heavy—The automatic insertion mechanism included within the device occupies substantial volume as described in U.S. Pat. No. 6,699,218, which is incorporated by reference herein. The patient must carry the heavy and bulky insertion mechanism during the entire usage of the pump.        
In view of the foregoing, what is needed is an improved method and device for delivery of therapeutic fluid to the body.